my 400mm 5.6 wont focus sharp

I have my camera (5d mkiv) set up on tripod and trigger with my 400mm lens. It is set up as one shot with the center focusing point. I take a picture in live view at 25m and it is pin sharp, however when i use normal position it is not as sharp, I have gone thru the micro settings from -10 to +10 but still cannot get it as sharp as live view. Any suggestions would be most welcome

This tells you it is not the lens or camera. That means you need to look elsewhere for the issue.

When you focus using Live View you are looking at excatgly what the sensor is recording. If its in focus in Live View it will be in focus in the digital file.

When you are focusing through the view finder you are indirectly focusing the lens; you cannot actually see whether it is in focus or not.

If its "pin sharp" in Live View but not when you use the "normal" AF system it means there is a problem in the phase-detection AF system "flowpath". It could be badly out of adjustment or damaged, so that camera repair is necessary, or it could just need autofocus micro adjustment "AFMA".

In "One Shot" mode the system only focuses until it achieves focus... then stops focusing. If anything moves after it achieved a focus lock, it does not re-focus unless you force it. In "AI Servo" mode it will continuously track focus.

As for focus points... if you force it to use a specific AF point, then that's the point it will use (you can also use AF point expansion or surround modes to increase the area, but again... it will stick to that cluster of points).

If you start to give the camera more freedom ... zone focus or allow all AF points... then the camera uses some rules to decide how to choose a focus point.

In typical One-Shot mode (if all AF points are active), it will typically try to find the AF point that can achieve focus at the CLOSEST focus distance to the camera. This means you would want to make sure there is are no focus points located on anything in the scene which is closer than your intended subject.

In AI Servo mode it will follow the rules based on the intelligent Tracking & Recognition system (iTR). You can do things such as set an initial point of interest and then select the "case" rule for how it should behave when trying to follow that subject around the frame and it will do its best to keep up. It will typically highlight (with a few squares) the points that are being tracked so you know what it thinks it is focused on. There are also rules about how it should behave when doing a burst of shots. Note that iTR is only active in viewfinder mode (not available if doing live-view) and also you must be using either zone-AF, large-zone-AF, or full auto-AF (all points active). It is not available if using spot, single-point, AF-expansion, or AF-surround modes.

If single-point AF nails focus for you... then my guess is when you say "normal position" you are letting the camera pick the AF point and when that happens, it has different rules to decide which AF point should be used. This isn't a big deal if you know the rules.